Crevasse splay morphodynamics in a dryland river terminus: Río Colorado in Salar de Uyuni Bolivia

Abstract

High-resolution satellite imagery in combination with field investigation enables the analysis of splay morphological developments in time and space at the low-gradient terminus of the modern Río Colorado dryland river system in the Salar de Uyuni (Bolivia). Two sets (2004/2005, 2010/2011) of satellite images are used to visualize splay morphological developments and three types of crevasse splays are identified based on temporal changes: (1) new crevasse splays (NCS), refers to those splays that are not observed in the first set of images but can be observed on the second sets of images; (2) changing crevasse splays (CCS), representing those splays that are found on the first set of images but their geometry has changed between two satellite observation periods; and (3) inactive crevasse splays (ICS), referred to those splays that are found on the first set of images but on the second set of images they remain the same, or are partially overlapped by adjacent expanding crevasse splays. The density or frequency of these three types of crevasse splays has no correlation with the distance to the starting point of the river or the local slope. The cross-sectional area of the studied river steadily decreases downstream, and frequency analysis shows a downstream increase in the number of crevasse splays and suggests an exponential relationship with the river cross-sectional area. Development of crevasse splays is often attributed to topographic lows between adjacent crevasse splays, and they fill in the depression by compensational stacking e.g. Li et al. (2014). These amalgamated splays are capable of forming a large area of sheet sands and potentially provide an analogue for thin-bedded hydrocarbon reservoirs.